In one of the best trades in team history, Baltimore acquired Tillman, Adam Jones and George Sherrill from the Seattle Mariners for pitcher Erik Bedard in February 2008. For three years, Tillman bounced between the majors and minors before breaking out in late 2012.

Tillman went 9-3 with a 2.92 ERA in 15 games in 2012. Last year, he was 16-7 with a 3.71 ERA, and the Orioles think he can improve even more.

"There's another level he can go to," Showalter said.

In his first three seasons with the Orioles, Tillman was 7-15 with an ERA well over five in each year.

The 25-year-old Tillman hopes to be the Opening Day starter on March 31 when Baltimore hosts the Boston Red Sox.

"I think it would be a big honor. I think it's a big deal," Tillman said.

Showalter won't name his first starter for a few weeks, but it is obvious that Tillman will be the man. He tries to avoid being presumptuous about being the staff leader.

"We've got five No. 1s. We're only as good as the starter that day," Tillman said.

Besides Tillman, the Orioles have Wei-Yin Chen, Miguel Gonzalez and Bud Norris in the rotation. The fifth starter isn't set.

"We've got a lot more than five guys capable of making the starting rotation this year. That's a good thing," Tillman said. "It creates competition. You thrive off that. Competition gets you going. I'm excited for the season."